1. Field of the Invention
The invention is generally related to powered hand tools used in surgical operations and, more particularly, to hand tools used in liposuction and lipoinjection procedures.
2. Background Description
Liposuction is a well known surgical procedure for surgically removing fat tissue from selected portions of a patient's body. Current practice is to make an incision and then insert a cannula in the space occupied by fat tissue. The cannula is then moved in such a manner as to mechanically break up the fat tissue. While moving the cannula, pieces of the fat tissue are aspirated from the space through the cannula by vacuum pressure from a syringe or pump. This technique requires significant effort on the part of the surgeon in terms of both the physical effort required to move the cannula back and forth, and the effort required to control the direction of movement of the cannula in order for fat tissue to be withdrawn only from specific areas of the patient's body. It would be advantageous to provide equipment which reduces the physical demands on the surgeon, and allows easier control of the direction of cannula movement.
U.S. Pat. No. 4,886,491 to Parisi et al. discloses a liposuction tool which utilizes an ultrasonic probe to break up the fat tissue. U.S. Pat. No. 5,295,955 to Rosen discloses a liposuction apparatus which employs microwave energy to soften fat tissue. The disadvantage of both these approaches is that they do not control the direction of liposuction, and can lead to withdrawing fat tissue unevenly, thus producing a lumpy surface upon completion of the surgery.
Swartz discloses, in U.S. Pat. Nos. 4,735,605, 4,775,365, and 4,932,935, power assisted liposuction tools which include an external sheath which houses a rotary driven auger type element. Fat tissue is selectively sheared at an opening in the external sheath by the auger element pulling tissue within the opening and shearing it off at the opening. In one of the designs, Swartz contemplates oscillating the direction of rotation of the auger element. U.S. Pat. No. 4,815,462 to Clark discloses a lipectomy tool which has an inner cannula with a knife edge opening which rotates within an outer cannula. In Clark, fat tissue is drawn by suction into an opening the outer cannula, and is then sheared off by the knife edge of the inner cannula and aspirated to a collection vessel. A disadvantage with each of these Swartz and Clark designs is that they tend to tear the tissue. This can be problematic when working in confined spaces near blood vessels and the like.
U.S. Pat. No. 5,112,302 to Cucin discloses a powered liposuction hand tool that moves a cannula back and forth in a reciprocating manner. Back and forth movement is akin to the movements made be surgeons, and is therefore a marked improvement over the rotary designs of Swartz and Clark. However, the Cucin design is fairly clumsy and requires the cannula and reciprocating mechanism to move within a portion of the hand held base unit.
U.S. Pat. No. 5,352 to Greco et al. describes an automated liposuction device with reciprocating cannula movement that is akin to Cucin's; however, this device relies on a pneumatic cyclinder drive system, with multiple sensors, and a computer controller to adjust and regulate the cannula movement. Overall, the Greco system is complex and subject to a variety of drive control problems, as well as high costs for various elements. In addition, the Greco system is designed to provide cannula stroke lengths which are in excess of 1 cm, which is not ideal in a number of different circumstances.
U.S. Pat. No. 5,348,535 to Cucin discloses another power assisted liposuction instrument similar to that shown in U.S. Pat. No. 5,112,302 to Cucin. The design in U.S. Pat. No. 5,348,535 utilizes movement of an internal sleeve within an external sleeve to shear off fat tissue pulled within an opening in the external sleeve. The design in U.S. Pat. No. 5,348,535 is complex in that it requires multiple sleeves, and the reciprocating movement causes periodic changes in the aspiration aperture. U.S. Pat. No. 4,536,180 to Johnson discloses a surgical system for suction lipolysis which employs an internal or external air conduit which directs airflow at or near the cutting tip of the cannula to enhance fat tissue clearance during aspiration through the cannula. U.S. Pat. No. 5,013,300 to Williams discloses suction lipectomy tool which allows suction control via the surgeons thumb covering and uncovering vent holes in the lipectomy tool housing.